Fig. 3: Changes in the global distribution of C4 vegetation between 2001–2019.
From: Mapping the global distribution of C4 vegetation using observations and optimality theory
Spatial distributions of changes in (a) total C4 vegetation, (c) C4 natural grasses and (e) C4 crops from 2001 to 2019; b The changes in the total area of C4 vegetation, C4 natural grasses and C4 crops, in percentages of global vegetated land surface; d the synergies of changes in C4 natural grasses and C4 crops, where ++ means both C4 natural grasses and C4 crops area abundance increased, − − means both decreased, + − means C4 natural grasses increased and C4 crops abundance decreased, − + means the opposite; f the drivers for the change in C4 natural grasses and C4 crops area abundances. Climate drivers include atmospheric CO2 concentration, air temperature (Tair), vapor pressure deficit (VPD) and soil moisture (SM) during the growing seasons. In (b), the uncertainty for C4 crop is 10% of the C4 crop area reported, the uncertainty for C4 natural grass area is the combination of the uncertainty in remote sensing-based grassland fraction and the uncertainty of the AC4/AC3 - C4 coverage relationship (Fig. 1b), and uncertainty for C4 vegetation is the combination of uncertainties of C4 crop and C4 natural grass areas.
